1. The Field of the Invention
The present invention relates to surgical tools. More specifically, the present invention relates to thermal surgical tools used in open and minimally invasive surgical procedures and interventional surgical and therapeutic procedures and methods for making the same.
2. State of the Art
Surgery generally involves cutting, repairing and/or removing tissue or other materials. These applications are generally performed by cutting tissue, fusing tissue, or tissue destruction. There are currently a number of electrosurgery modalities used for cutting, coagulating, desiccating, ablating, or fulgurating tissue, which have undesirable side effects and drawbacks. These include monopolar and bipolar electrosurgery modalities, electrocautery resistive heating elements, ferrite beads and alloy mixes in ceramics, lasers, and microwave antenna.
Tissue destruction instruments generally heat tissue to a predetermined temperature for a period of time to kill, or ablate, the tissue. However, each of these modalities has inherent disadvantages.
A significant improvement in electrosurgery was developed wherein a thin ferromagnetic coating is placed over a conductor. As an oscillating electrical energy source is passed through the conductor, inductive and/or other types of heating may be caused in the ferromagnetic coating. Moreover, the surgeon may be able to quickly turn the surgical or therapeutic tool on and off due to a small heat latency in the thin ferromagnetic coating. A detailed discussion of the design and use of ferromagnetic surgical instruments is contained in U.S. Patent Publication Nos. 2010-0268207, 2010-0268214, 2010-0268208, 2010-0268209, 2010-0268215, 2010-0268205, 2010-0268210, 2010-0268212, 2010-0268213, 2010-0268211, and 2010-0268216, 2010-0268206, which are applications related to the present application and are incorporated herein by reference.
One challenge with ferromagnetic electrosurgery instruments is obtaining a proper rigidity in the working element, and in ensuring proper conductivity and attachment of the ferromagnetic layer. While some materials work well for rigidity, such as tungsten, their less desirable conductivity may cause resistive heating in the conductor. This can create latent heat in the electrosurgical instrument and reduce the ability of the instrument to cool down when the working element is not active.
Additionally, some materials are difficult to securely attach the ferromagnetic material to. If the ferromagnetic material does not adhere well, there is a risk of some of the material coming off in the patient.
Still another concern with electrosurgical instruments is that the material should be biocompatible. While some materials work well as a ferromagnetic coating to create the desired heat, they may not be desirable for direct contact with human tissues. Thus, there is a need for an improved ferromagnetic electrosurgical instrument.